1.1 More information on ‘landslide form’

There are several morphological features that can be recognized to a greater or lesser extent in most landslides. The uppermost part is the depletion or concave zone (erosional, generating or failure zone) where slope material has failed and become displaced downslope. In some cases the displacement may be only a few metres while in others the failure zone will be completely evacuated to expose the surface of rupture and to leave a distinctive scar on the hillslope.

Fig. 1. Image commonly used to illustrate the part of a landslide (from Varnes, 1978)
Fig. 2. Translational rock slide, occured in Novembre 1994 in the Langhe Hills (Piemonte Region), in which can be clearly distiguished the main scarp, the flanks and the displaced material (photo from Archivio CNR-IRPI, Torino)

The displaced mass may remain close to the failure zone or it may continue to travel downslope leaving a transport track ending in a colluvial accumulation zone or acting as a supply to some other geomorphic agent (e.g. river, sea or glacier). The distance that landslide material travels (runout) is a characteristic of the type of land- slide. For example, controlled by the height of fall and volume, rock avalanches can travel at high velocity for several kilometres. Runout distance and velocity for other types of landslide are controlled by factors such as volume, slope angle and morphology, clay content, water content, and surface frictional characteristics of the runout pathway.

For the references herein and for knowing sources of didactic material go to 1.3 Selected references